[Below is the original script. But a few changes may have been made during the recording of this audio podcast.]

Going home for Thanksgiving is a time-honored American tradition—and one that exemplifies the environmental burden created by all our hectic traveling. We spewed more than 2 billion metric tons of carbon dioxide from our trains, planes and automobiles in 2007, according to the U.S. Department of Energy.

I love my beat up old junker of a car, but at 30 miles-per-gallon, I'm not doing the atmosphere any favors. Turning to ethanol or biodiesel doesn’t help much, given that those fuels from crops mean less food: hardly in keeping with the Thanksgiving tradition.

Another type of biofuel, however, may be the only hope for reining in airplane emissions. Whether made from shrubs like jatropha or, even better, algae that can thrive on dirty water, bio-kerosene is being tested by everyone from the U.S. Air Force to Air New Zealand, as well as jet engine-makers Boeing and Rolls Royce.

So the best existing transportation option is an old-fashioned one: trains. Not only have trains been hybrid since before it was cool (i.e. the 1950s) they carry a lot more passengers for every gallon of diesel burned. So if you have a choiceamong planes, trains and automobiles...chugga chugga choo choo!